This invention relates to a liquid crystal antidazzle mirror used for a vehicle.
A liquid crystal antidazzle mirror which utilizes a liquid crystal is used as one type of an antidazzle mirror in an automobile. This liquid crystal antidazzle mirror alters the light transmission factor of the liquid crystal by controlling a voltage applied to the liquid crystal disposed in front of a mirror to control the reflectivity of the mirror, thereby performing the antidazzle action.
This liquid crystal antidazzle mirror described above necessitates a power source for driving the liquid crystal in principle of the operation. An automotive battery is generally used as this power source for the antidazzle mirror, but it is desirable to supply electric power from the battery only in case of using the antidazzle mirror so as to protect the battery against its discharge since the capacity of the battery is limited. The inventor of this invention has proposed a prior liquid crystal antidazzle mirror which has solved the problem of a decrease in the capacity of the automotive battery as disclosed in Japanese Utility Model Application No. 169708/1984. This liquid crystal antidazzle mirror is constructed, as shown in FIG. 2, of a liquid crystal drive control circuit 32 for controlling a voltage applied to a liquid crystal 31, and a power switch 34 cooperated with a key cylinder is connected between the control circuit 32 and a battery 33, and a key plate is plugged in a key cylinder as a so-called power is supplied only in the vehicle available state.
The abovementioned prior liquid crystal antidazzle mirror is effective in energy-saving since supplying power from the battery only when the power is supplied only in the vehicle available state. However, since the power supply is interrupted simultaneously when the power switch 34 is opened, the control circuit 32 is reset to the special predetermined initial set mode of antidazzle mode on dazzle mode. Thus, in the conventional antidazzle mirror, even if the power switch is closed to use again the vehicle immediately after the power switch is opened or within little time from when the switch is opened, it is difficult to effectively reset the mode of the antidazzle mirror to the used mode immediately before the power switch is opened. In general, when the vehicle is used immediately after the power switch is opened or within short time after the power switch is opened, it is normal that the circumstances around the vehicle do not almost change. Thus, it is desired to reset the mode of the antidazzle mirror to the used mode immediately before the power switch is opened simultaneously when the power switch is closed. As described above, since it is impossible in the conventional liquid crystal antidazzle mirror to the used mode immediately before the power switch is opened when the power switch is again used, the desired mode must be obtained by operating the mode change switch whenever the power switch is closed.